Methods and systems for providing direct DMA

ABSTRACT

A method and system for efficient direct DMA for processing connection state information or other expediting data packets. One example is the use of a network interface controller to buffer TCP type data packets that may contain connection state information. The connection state information is extracted from a received packet. The connection state information is stored in a special DMA descriptor that is stored in a ring buffer area of a buffer memory that is accessible by a host processor when an interrupt signal is received. The packet is then discarded. The host processor accesses the ring buffer memory only to retrieve the stored connection state information from the DMA descriptor without having to access a packet buffer area in the memory.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/690,069, filed Jan. 16, 2009, which claims the benefit of U.S.Provisional Patent Application Ser. No. 61/205,384, filed on Jan. 16,2009, each of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure generally relates to packet transmission fornetworks and more particularly, to a system and method for use of directDMA for efficient packet transmission between a network interfacecontroller and a host processor.

BACKGROUND

The use of server-based applications for remote clients over a networkhas become ubiquitous. With the widespread use of diverse serverapplications, different needs for devices such as a network interfacecontroller to facilitate data received through the network to the serverhave arisen. The function of such a network interface controller is toprocess a direct memory access (DMA) to store received packets over thenetwork and notify the host processor via an interrupt of the storedinformation. Since interrupts are computationally expensive, it isdesirable to interrupt a processor on a server only when necessary andnetwork interface controllers are designed to optimize this process.

Currently, the DMA is the method by which a host processor accessesstored network packets after receiving interrupts from the networkinterface controller of a network traffic management device. The DMA ofa packet to the host processor involves the network interface controllerwriting a received packet into a packet buffer area in the host memoryin which the host processor accesses the host memory to retrieveinformation contained in the received data packets. The packet buffer israndomly accessible by the host processor, but requires greaterprocessing resources and is generally a slower access because the packetbuffer area is typically DRAM. Typically, a descriptor with a pointer tothe packet buffer area is written into a ring buffer area, whereby thering buffer area is smaller than the packet buffer area and allows forfaster access by the host processor. Once the descriptor is written intothe ring buffer area, the host processor is notified and the hostprocessor then reads the descriptor in the ring buffer area to retrievethe packet buffer pointer. The host processor then reads the stored datapacket from the location, indicated by the pointer, in the packet bufferarea and reads the contents of the data packet.

Packets received and processed by the host processor are frequently TCPpackets, many of which generally contain only connection stateinformation and have no payload or attached data. Such TCP packets aretypically SYN, ACK, FIN and RESET packets. A TCP packet havingconnection state information, which includes a few flags and fields, isvery small relative to the overall size of a TCP packet with attachedpayload data. Current systems which handle packets with connection stateinformation as well as packets with payload data are inefficient becausethe host processor cannot distinguish between the two different types ofpackets. This results in the host processor having to access thedescriptor in the ring buffer area and then access the packet bufferarea in order to just to receive the connection state information inmany TCP packets. This results in a significant use of computational andprocessing resources for the host processor to access the packet bufferarea to only process connection state information of a TCP packet. Theinefficiency is compounded by the fact that the access to the packetbuffer area is likely to be a CPU cache miss resulting in an expensiveDRAM memory access.

SUMMARY

In an aspect, a method for efficiently processing a received data packetcomprises reading a received data packet to determine if the data packetcontains connection state information. The connection state informationis extracted from the data packet if the data packet contains theconnection state information. The extracted connection state informationis stored as a special DMA descriptor in a ring buffer memory accessibleby a host processor. The host processor is notified that the special DMAdescriptor has been stored in the ring buffer memory. The host processoris then able to immediately access the ring buffer memory to retrievethe stored connection state information from the special DMA descriptor.

In another aspect, a computer or other machine readable medium havingstored thereon instructions for efficiently processing a received datapacket comprising reading a received data packet to determine if thedata packet contains connection state information. Connection stateinformation is extracted from the data packet if the data packetcontains the connection state information. The extracted connectionstate information is stored as a special DMA descriptor in a ring buffermemory accessible by a host processor. The host processor is notifiedthat the special DMA descriptor has been stored in the ring buffermemory, wherein the host processor is able to immediately access thering buffer memory to retrieve the stored connection state informationfrom the special DMA descriptor.

In yet another aspect, a network traffic management device includes oneor more processors, a memory coupled to the one or more processors by abus, and a network interface controller coupled to the one or moreprocessors and the memory and be capable of receiving and forwardingdata packets from a network that relate to a plurality of applications.At least one of the one or more processors is configured to executeprogrammed instructions stored in the memory and one or more processorswith logic is configured to implement reading a received data packet todetermine if the data packet contains connection state information. Theconnection state information is extracted from the data packet if thedata packet contains the connection state information. The connectionstate information is stored as a special DMA descriptor in a ring buffermemory configured to be accessible by a host processor. The hostprocessor is notified that the special DMA descriptor has been stored inthe ring buffer memory and is able to immediately access the ring buffermemory to retrieve the stored connection state information from thespecial DMA descriptor.

Additional aspects will be apparent to those of ordinary skill in theart in view of the detailed description of various embodiments, which ismade with reference to the drawings, a brief description of which isprovided below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a network system using one example of anetwork interface controller using a direct DMA process;

FIG. 2 is a block diagram of the example network traffic managementdevice in FIG. 1 that uses a direct DMA process to allow efficientprocessing of packets;

FIG. 3 is a detailed block diagram of the example network trafficmanagement device in FIG. 1 that uses a direct DMA process to allowefficient processing of packets;

FIG. 4 is a flow chart of a method for optimizing received stateconnection packets for processing by the example network trafficmanagement device in FIG. 1; and

FIG. 5 is a flow chart of a method for direct DMA handling of differenttypes of packets to avoid the host processor accessing the packet bufferarea for state connection packets.

DETAILED DESCRIPTION

Currently, existing network interface controllers and host processorsrequire unnecessary access to packet buffer area memory for TCP packetswith connection state information or other types of information whichare to be immediately consumed by the host processor. The access tobuffer memory for such TCP packets consumes significant host processorresources and results in slower processing of the packets. The describedtechnology reduces this by allowing the network interface controller ofthe network traffic management device to provide DMA services to thehost processor via one or more DMA channels in which the one or more DMAchannels supports the movement of data traffic between the networktraffic management device and the host processor main memory system.

Referring now to FIG. 1, an example system environment 100 employs anetwork traffic management device (also referred to as “trafficmanagement device”) 110 that includes a network interface controller andone or more processors capable of manipulating those data packets thathave connection state information and applying DMA for those datapackets. In applying DMA to the data packets with connection stateinformation, a special descriptor is written into the ring buffer areain a buffer memory in the network traffic management device 110. Thenetwork interface controller within the network traffic managementdevice 110 notifies one or more host processors of this specialdescriptor in which the host processor accesses the ring buffer andprocesses the special descriptor immediately. The host processor isthereby able is quickly obtain the connection status information withouthaving to access the packet buffer memory.

The example system environment 100 includes one or more servers 102(e.g., Web application servers), one or more client devices 106 and thetraffic management device 110, although the environment 100 can includeother numbers and types of devices in other arrangements. The trafficmanagement device 110 is coupled to the servers 102 via local areanetwork (LAN) 104 and client devices 106 via a network 108. Generally,requests sent over the network 108 from client devices 106 towardsservers 102 are handled by the traffic management device 110.

Client devices 106 comprise computing devices capable of connecting toother computing devices, such as network traffic management device 110and servers 102. Communications between the client devices 106, networktraffic management device 110 and servers 102 occur over wired and/orwireless networks, such as network 108, to send and receive data.Non-limiting and non-exhausting examples of such devices includepersonal computers (e.g., desktops, laptops), mobile and/or smart phonesand the like. In this example, client devices 106 run Web browsers thatmay provide an interface for operators, such as human users, to interactwith for making requests for resources to different web server-basedapplications or Web pages via the network 108, although other serverresources may be requested by clients. One or more Web-basedapplications may run on the server 102 that provide the requested databack to one or more exterior network devices, such as client devices106.

Network 108 comprises a publicly accessible network, such as theInternet in this example, although the network 108 may comprise othertypes of private and public networks that include other devices.Communications, such as requests from clients 106 and responses fromservers 102, take place over the network 108 according to standardnetwork protocols, such as the HTTP and TCP/IP protocols in thisexample. However, the principles discussed herein are not limited tothis example and can include other protocols. For instance, network 108may provide responses and requests according to the HTTP-basedapplication RFC protocol or the CIFS or NFS protocol in an example.

Further, it should be appreciated that network 108 may include localarea networks (LANs), wide area networks (WANs), direct connections andany combination thereof, as well as other types and numbers of networktypes. On an interconnected set of LANs or other networks, includingthose based on differing architectures and protocols, routers, switches,hubs, gateways, bridges, and other intermediate network devices may actas links within and between LANs and other networks to enable messagesand other data to be sent to and from the network devices. Also,communication links within and between LANs and other networks typicallyinclude twisted wire pair (e.g., Ethernet), coaxial cable, analogtelephone lines, full or fractional dedicated digital lines includingT1, T2, T3, and T4, Integrated Services Digital Networks (ISDNs),Digital Subscriber Lines (DSLs), wireless links including satellitelinks and other communications links known to those skilled in therelevant arts. In essence, the network 108 includes any communicationmedium and method by which data may travel between the client devices106, the servers 102 and the network traffic management device 110, andthese are provided by way of example only.

LAN 104 comprises a local area network that includes the network trafficmanagement device 110 coupled to the one or more servers 102. However,the LAN 104 may comprise other types of private and public networks withother devices. Networks, including local area networks, besides beingunderstood by those skilled in the relevant arts, have already beengenerally described above in connection with network 108 and will not bedescribed further here.

Server 102 comprises one or more server computing machines capable ofoperating one or more applications (e.g., Web-based applications) thatmay be accessed by network devices in the network 108, such as clientdevices 106, via the network traffic management device 110, and mayprovide other data representing requested resources, such as particularweb page(s), image(s) of physical objects, and any other objects,responsive to the requests, although the server 102 may perform othertasks and provide other types of resources. It should be noted thatwhile only two servers 102 are shown in the environment 100 depicted inFIG. 1, other numbers and types of servers may be coupled to the networktraffic management device 110. It is also contemplated that one or moreof the Web application servers 102 may be a cluster of servers managedby the network traffic management device 110.

As per the TCP/IP protocols, requests from the requesting client devices106 may be sent as one or more streams of data packets over network 108to the traffic management device 110 and/or the servers 102 to establishconnections, send and receive data for existing connections, and forother purposes. With other protocols, such as the ICMP protocol, datapackets may be sent which indicate that an error has occurred or that aspecific event is to be immediately consumed by the traffic managementdevice 110. It is to be understood that the one or more servers 102 maybe hardware and/or software, and/or may represent a system with multipleservers that may include internal or external networks. In this example,the servers 102 may be any version of Microsoft® IIS servers or Apache®servers, although other types of servers may be used. Further,additional servers may be coupled to the network 108 and many differenttypes of applications may be available on servers coupled to the network108.

Each of the servers 102 and client devices 106 may include one or morecentral processing units (CPUs), one or more computer readable media(i.e., memory), and interface systems that are coupled together byinternal buses or other links as are generally known to those ofordinary skill in the art; as such, they will not be described furtherhere.

As shown in the example environment 100 depicted in FIG. 1, the networktraffic management device 110 is interposed between client devices 106in network 108 and servers 102 in LAN 104 in an asymmetricconfiguration, although other numbers of network traffic managementdevices 110 can be used, such as a symmetric configuration. Again, theenvironment 100 could be arranged in other manners with other numbersand types of devices. Also, the network traffic management device 110 iscoupled to the network 108 by one or more network communication linksand intermediate network devices, such as routers, switches, gateways,hubs and other devices (not shown). It should be understood the devicesand the particular configuration shown in FIG. 1 are provided forexemplary purposes only and are therefore not limiting.

Generally, the network traffic management device 110 manages networkcommunications, which may include one or more client requests and serverresponses, from/to the network 108 between the client devices 106 andone or more of the servers 102 via the LAN 104. These requests may bedestined for one or more servers 102, and for example, may take the formof one or more TCP/IP data packets originating from the network 108,passing through one or more intermediate network devices and/orintermediate networks, until ultimately reaching the traffic managementdevice 110. In any case, the network traffic management device 110 maymanage the network communications by performing several network trafficrelated functions involving the communications, in particular direct DMAfor efficient packet transmission and access. It should be noted thatalthough TCP data packets are referred to herein, other network and/ornon-network based protocols are contemplated. For instance, the datapackets that are processed and manipulated by the network trafficmanagement device may be RTSP control frames, SETP protocols, UDP, ICMPor any other protocol which requires DMA of state information withoutbulk or payload data or requires that the data packet be consumedimmediately.

Referring now to FIG. 2, an example network traffic management device110 includes a network interface controller 200, one or more device I/Ointerfaces 202, and a host processor complex 218, which are coupledtogether by bus 208, although the device 110 could include other typesand numbers of components. As will be discussed in more detail below,the host processor complex 218 desirably includes one or more hostprocessors 220 as well as a memory (also referred to herein as buffermemory) 219 which will be discussed in more detail below. The one ormore host processors 220, as discussed in FIG. 3, are configured toexecute computer/machine readable and executable instructions stored indevice memory 219 to implement network traffic management relatedfunctions of the network traffic management device 110, including thetechnology described and illustrated herein. It should be noted thatalthough more than one host processor 220 may be present in the networktraffic management device 110, “a host processor” is referred to hereinfor clarity purposes and can be construed as meaning one or more hostprocessors.

The host processor 220 comprises logic to configured to execute one ormore aspects of the technology described herein, although other mannersfor implementing this technology can be used. The host processor 220may, by way of example only, comprise other types and/or combinations ofapplication specific integrated circuits (“ASICs”), programmable logicdevices (“PLDs”), field programmable logic devices (“FPLDs”), fieldprogrammable gate arrays (“FPGAs”), and the like, programmed orconfigured according to the teachings as described and illustratedherein. As shown in FIGS. 2 and 3, the network traffic management device110, through use of the network interface controller 200 and the hostprocessor complex 218, manipulates the data packets and communicateswith the server 102 to achieve efficient processing of the data packetswith connection state information, event information, error messages, orother information which is to be consumed immediately by the hostprocessor 220.

Device I/O interfaces 202 comprise one or more user input and outputdevice interface mechanisms, such as a computer keyboard, mouse, displaydevice, and the corresponding physical ports and underlying supportinghardware and software to enable the network traffic management device110 to communicate with the outside environment for accepting user datainput and to provide user output, although other types and numbers ofuser input and output devices may be used. Alternatively oradditionally, the network traffic management device 110 may communicatewith the outside environment for certain types of operations (e.g.,configuration) via a network management port, for example.

Network interface 204 comprises one or more mechanisms that enablenetwork traffic management device 110 to engage in TCP/IP communicationsover LAN 104 and network 108. However, the network interface 204 may beconstructed for use with other communication protocols and types ofnetworks. Network interface 204 is sometimes referred to as atransceiver, transceiving device, or network interface card (NIC). Thenetwork interface 204 transmits and receives network data packets to oneor more networks, such as LAN 104 and network 108 in this example.

The network interface controller 200 executes and controls the directDMA to the buffer memory 219 and communicates with the host processor220 in the network traffic management device 110. In an aspect where thenetwork traffic management device 110 includes more than one networkinterface controller 200 (or a network interface controller 200 that hasmore than one core), each network interface controller 200 (and/or core)may use the same single network interface 204 or a plurality of networkinterfaces 204. Further, the network interface 204 may include one ormore physical ports, such as Ethernet ports, to couple the networktraffic management device 110 with other network devices, such asservers 102. Moreover, the network interface 204 may include certainphysical ports dedicated to receiving and/or transmitting certain typesof network data, such as device management related data for configuringthe network traffic management device 110.

Bus 208 may comprise one or more internal device component communicationbuses, links, bridges and supporting components, such as bus controllersand/or arbiters. The bus 208 enables the various components of thenetwork traffic management device 110, such as the network interfacecontroller 200, device I/O interfaces 202, network interface 204, one ormore processors 220 and a device or buffer memory 218, to communicate.It should be noted that the bus 208 may enable one or more components ofthe network traffic management device 110 to communicate with componentsin other devices as well. By way of example only, the bus 208 mayinclude HyperTransport, PCI, PCI Express, InfiniBand, USB, Firewire,Serial ATA (SATA), SCSI, IDE and AGP buses, although other types andnumbers of buses may be used and the particular types and arrangement ofbuses will depend on the particular configuration of the network trafficmanagement device 110.

The buffer memory 219, in general, comprises computer readable media,namely computer readable or processor readable storage media, which areexamples of machine-readable storage media. Computer readablestorage/machine-readable storage media may include volatile,nonvolatile, removable, and non-removable media implemented in anymethod or technology for storage of information. Such media examplesinclude computer readable/machine-executable instructions, datastructures, program modules, or other data, which may be obtained and/orexecuted by one or more processors, such as one or more host processors220. The one or more host processors 220 and/or the network interfacecontroller 200 may perform actions, including implementing an operatingsystem for controlling the general operation of network trafficmanagement device 110 to manage network traffic and provide direct DMAfor efficient packet transmission as described herein.

Examples of computer readable storage media include RAM, BIOS, ROM,EEPROM, flash/firmware memory or other memory technology, CD-ROM,digital versatile disks (DVD) or other optical storage, magneticcassettes, magnetic tape, magnetic disk storage or other magneticstorage devices. Computer readable storage media may be any other mediumwhich can be used to store the desired information, including dataand/or computer/machine-executable instructions, and which can beaccessed by a computing or specially programmed device, such as networktraffic management device 110. When the instructions stored in thebuffer memory 219 are run by the one or more host processors 220, thenetwork traffic management device 110 performs at least a portion of theprocesses in described herein as well as other various network trafficmanagement related functions, including firewall functions, server loadbalancing functions, device configuration functions (e.g., definingnetwork security policies), and other functions.

FIG. 3 illustrates a block diagram of the network traffic managementdevice 110 in accordance with an aspect of the present disclosure. Thenetwork interface controller 200 within the network traffic managementdevice 110 bridges data traffic between the host processor complex 218and one or more network interfaces 204. As stated above, the hostprocessor complex 218 includes the host processor 220 as well as one ormore buffer memories 219 interconnected by one or more internal bus 217.It is contemplated that the host processor complex 218 can also includeadditional components, for example, additional processors, controllersand electronic circuitry to handle data. The network interfacecontroller 200 connects to the host processor complex 218 over thepacketized CPU bus 208. DMA services are provided between the networkinterface controller 200 and the host processor complex 218 via one ormore DMA channels 227, 229. It should be noted that although only twoDMA channels 227, 229 are shown in FIG. 3, any number of DMA channelsare contemplated. Each DMA channel supports the movement of data trafficbetween the I/O devices and the buffer memory 219 in the host processorcomplex 218. One or more DMA channels 227 or 229, can access any of theattached I/O devices through the network interface controller 200'sinternal switching matrix.

As will be discussed in more detail below, the buffer memory 219 storesthe received network packets from the network interface controller 200and directional pointers that indicate the location in the buffer memory219 of the stored packet. The host processor 220 accesses the buffermemory 219 via interrupts for direct memory accesses to data stored indifferent locations of the buffer memory 219 via the packetized CPU bus208. Using DMA channels 227, 229, network packets received over thenetwork 108 are written into the buffer memory 219 by the networkinterface controller 200 via the packetized CPU bus 208 after beingsplit into constituent CPU bus packets. For transmitting network packetsto the network 108 using DMA channels 227, 229, the CPU bus packets areread from buffer memory 219 and reassembled over the CPU bus 208 intonetwork packets.

The DMA channels 227 and 229 are utilized to access the memory 219 ofthe network traffic management device 110. The network interfacecontroller 200 in this example interfaces the processor 220 and buffermemory 219 via the packetized CPU bus 208 and to the network 108 via anEthernet link 206. The network interface controller 200 providesmultiple DMA channels 227, 229 that couple the interface port 202 atwhich network packets are received to the CPU bus interface 204. Networkpackets are segmented into smaller CPU bus packets and sent over thepacketized CPU bus 208 in an interleaved manner for processing by thehost processor complex 218.

The packetized CPU bus 208 used by the network interface controller 200in this example segments and/or reassemble the network packets obtainedfrom one or more of the DMA channels, e.g., DMA channels 227 and 229.The obtained network packets from the DMA channels 227 and 229 can besegmented and/or reassembled into smaller associated or constituentpackets, e.g., HyperTransport packets, to be transmitted over thepacketized CPU bus 208. In one example, the maximum CPU bus packet sizeis 64 bytes, but of course other sizes can be used for the CPU buspacket size. The network packets may be segmented into multiple CPU buspackets and sent across the packetized CPU bus 208. For example, asimple network packet of 128 bytes may be segmented into twoHyperTransport packets, with each HyperTransport packet being 64 bytes.Of course, other segmenting schemes can be used depending upon the sizeof the network packet and the size of the individual HyperTransportpackets. The number of HyperTransport packets needed to send the entirenetwork packet is a function of the size of the network packet and thesize of the HyperTransport packets.

Similarly, in the reverse direction for transmitting network packetsfrom the network traffic management device 110 to client computers 106or to servers 102 via network 108 or LAN 104, respectively, CPU buspackets are reassembled into network packets using DMA channels 227, 229and transmitted via network port 202 over the Ethernet link 206. The DMAchannels 227 and 229 in the network interface controller 200 maintainsan independent segmentation and reassembly context. The CPU bus packetstream to and from each DMA channel 227 and 229 is fairly interleavedinto at least one stream over the packetized CPU bus 208 based uponvarious schemes, e.g., round robin, by way of example only.

The buffer memory 219 includes a packet buffer area 224, which isnon-contiguous, and a ring buffer area 226, which is dedicatedcontiguous memory space. In this example, the packet buffer area 224 islarger in capacity in comparison to the ring buffer 226, but has higheraccess cost memory such as in DRAM or related types of memory. Incontrast, the ring buffer area 226 may be a faster access memory but issmaller in capacity in comparison to the packet buffer area 224. Asshown in FIG. 3, data packets 228 and 230 are written and stored in thepacket buffer area 224 of the buffer memory 219. Respective DMAdescriptors 232 and 234 for the packets 228 and 230 are written by thenetwork interface controller 200 and stored in the ring buffer area 226.As will be discussed in more detail below, the network interfacecontroller 200 writes and stores a special DMA descriptor 236 into thering buffer area 226 in which the special DMA descriptor 236 representsa data packet having connection status information. Although the packets228 and 230 are shown written consecutively for convenience in FIG. 3,it is to be understood that the packets 228 and 230 may be written inany order in any part of the packet buffer area 224. The descriptors232, 234, and/or special DMA descriptor 236 may be written, for example,in a linear order in the ring buffer area 226.

The special DMA descriptor 236 is used for a direct DMA feature for datapackets that contain connection status information. In particular, thespecial DMA descriptor 236 contains the connection status information,and considering that the special descriptor 236 is written in the ringbuffer area 226, the processor 220 can quickly access the ring bufferarea 226 to obtain the connection status information without having toaccess the packet buffer area 224. The special DMA descriptor 236functions the same as a normal DMA descriptor described above except thespecial DMA descriptor 236 is larger than the descriptor for a normalDMA. The special descriptor may be used to store certain informationfrom the packet, however the entire packet is not copied into thedescriptor. In an example, only the significant protocol state changeinformation or connection status information is copied into the specialDMA descriptor 236. Data packets that use direct DMA must meet thecorrect classification profile in that they include the correct protocol(TCP for example) and no payload data. Thus, the data packet havingconnection status information will be instantly and entirely processedby the host processor 220 rather than being stored in the packet bufferarea 224 and later retrieved. In other words, by classifying the datapacket based on its desired contents (here, connection statusinformation) and associating a special descriptor to that data packet,the data packet is quickly and efficiently processed to achieve aperformance gain in processing time, as discussed below.

Thus, the network interface controller 200 classifies the data packetupon reading the contents of the data packet to determine whether thepacket includes connection state information, event information, errormessages, or other information which is to be consumed immediately bythe host processor 220. The network interface controller 200 will alsowrite the special DMA descriptor 236 and store the special DMAdescriptor 236 in the ring buffer area 226 of the memory 219. Thenetwork interface controller 200 will also notify the host processor 220via an interrupt signal that the special DMA descriptor 236 has beenwritten to the ring buffer area 226. A timer may be used to monitor theamount of time that the special DMA descriptor 236 remains in the ringbuffer area 226. The special DMA descriptor 236 will store pure protocolinformation that will be immediately accessed and consumed or processedby the host processor 220. This avoids having to copy the user data outof the descriptor ring buffer 226 and store it somewhere else, such asexpensive packet buffer area 224. The remaining portion of the datapackets using the direct DMA are discarded by the network interfacecontroller 200 and not transferred to the buffer memory 219.

The network interface controller 200 allows the host processor 220 toaccess the buffer memory 219. The packets 228 and 230 stored in thepacket buffer area 224 of the memory 219 are referenced via pointers 242and 244 which are stored in the respective DMA descriptors 232 and 234.Incoming packets with data in the payload field such as the packets 228and 230 may be written to the packet buffer area 224 by the networkinterface controller 200 for handling by the appropriate processor inthe host processor complex 218 via a normal DMA when an interrupt signalis sent. A pointer to the location of the packet in the packet bufferarea 224 is stored with the respective DMA descriptors 232 and 234 ofthe stored packets 228 and 230. The pointers such as the pointers 242and 244 are used to direct the host processor 220 to access the correctpart of the packet buffer area 224 and retrieve the stored packets forprocessing.

In the case of a data packet that has connection state information,event information, error messages, or other information which is to beconsumed immediately by the host processor 220, the direct DMA processutilized by the network interface controller 200 in the network trafficmanagement device 110 eliminates the need for the host processor 220 toaccess the packet buffer area 224 to retrieve that information. Thenetwork interface controller 200 may classify the type of data packet asa normal data packet with an attached payload and handle the data packetnormally without using direct DMA. However, if the network interfacecontroller 200 determines the data packet to include connection stateinformation 246 (such as SYN, ACK, FIN or RESET), event information,error messages, or other information which is to be consumed immediatelyby the host processor 220, the network interface controller 200 of thenetwork traffic management device 110 writes the special DMA descriptor236 containing that information into the ring buffer area 226. Uponnotification, the host processor 220 needs only to access the ringbuffer area 226 to retrieve the information which is to be consumedimmediately.

In this example, the network interface controller 200 may inspect eachpacket and determine if the packet is a TCP connection state onlypacket. The network interface controller 200 may be configured todetermine whether the packet contains event information, ICMP errormessages, or any other information which needs to be consumed by thehost processor 200. In the example in which the data packet contains TCPbased connection status information, the network interface controller200 extracts the applicable connection state information such as a SYN,ACK, FIN or RESET state indicator. A special DMA descriptor 236 is thencreated by the network interface controller 200 which writes the specialDMA descriptor 236 into the ring buffer area 226 of the memory 219. Thespecial DMA descriptor 236 contains the connection state informationpreviously extracted from the data packet, but does not contain a packetbuffer pointer since the full packet is discarded and not written in thepacket buffer area 224.

The described process may result in a large performance gain in thenetwork traffic management device 110 when the network traffic seen bythe network traffic management device 110 includes a large number ofconnection state packets. The large performance gain results at leastpartially from the saving of internal bus bandwidth that does not needbe used for accessing the packet buffer area 224. The gain also resultsfrom saving cache misses as the host processor 220 stops looking foraccess to the packet buffer area 224 because the special DMA descriptor236 contains all the information the host processor 220 needs for thatparticular data packet. The performance gain also results from avoidingthe expensive access to slower memory, such as DRAM or related types ofmemory, that is typically used for the packet buffer area 224.

The operation of the example direct DMA process, which may be run on thenetwork interface controller 200 of the network traffic managementdevice 110, will now be described with reference to FIGS. 2 and 3 inconjunction with the flow diagrams shown in FIG. 4-5. The flow diagramin FIGS. 4-5 is representative of example machine readable instructionsfor implementing the direct DMA process performed by the networkinterface controller 200 in the network traffic management device, andmore particularly the packet DMA channels 227, 229. It should be notedthat the functions are described herein as being performed by thenetwork traffic management device 110 may be performed by the networkinterface controller 200, the host processor 220 or a combination of thetwo components.

FIG. 4 is a flow diagram of a method for optimizing received stateconnection packets for processing by the example network trafficmanagement device 110 in accordance with an aspect of the presentdisclosure. In FIG. 4, the network traffic management device 110receives one or more packets of data (block 300) and reads the packettype of the one or more packets of data (block 302) to classify the datapacket based on whether the data packet contains information which is tobe consumed immediately by the host processor 220. In the event that thedata packet contains TCP based connection status information, he networktraffic management device 110 determines whether the data packetcontains the connection state information packet (block 304) (e.g. SYN,ACK, FIN or RESET). If the packet is not and/or does not contain aconnection state information packet, the network traffic managementdevice 110 will write the packet into the packet buffer area 224 of thememory 219 (block 306). The network traffic management device 110 willalso write a DMA descriptor in the ring buffer area 226 along with acorresponding pointer which points to the location in the packet bufferarea 224 where the written packet is contained (block 308). The networktraffic management device 110 will then end the process.

However, if the network traffic management device 110 determines andclassifies the data packet as having connection state information (block304), the network traffic management device 110 will extract theconnection state information from the packet (block 310). The networktraffic management device 110 will then write the connection stateinformation in a special DMA descriptor 236 which is written and storedin the ring buffer area 226 (block 312). The network traffic managementdevice 110 will then discard the packet (block 314) and end the process.It should be noted that the above functions are generally described asbeing performed by the network traffic management device 110 may beperformed by the network interface controller 200, the host processor220 or a combination of the two components.

FIG. 5 is a flow diagram of the interrupt process initiated by thenetwork traffic management device 110 to initiate the processing of adata packet or packets by the host processor 220. The network trafficmanagement device 110 initiates the process by sending an interruptsignal to the host processor 220 to notify the host processor 220 that adata packet has been written to the buffer 219 (block 350). In responseto receiving the interrupt signal, the host processor 220 accesses thering buffer 226 in the memory and reads the next DMA descriptor (block352). The host processor 220 determines whether the DMA descriptor is aspecial DMA descriptor (block 354) as discussed above. If the hostprocessor 220 determines that the identified DMA descriptor is not aspecial DMA descriptor 236, the host processor 220 will proceed to readthe corresponding pointer in the DMA descriptor (block 356). The hostprocessor 220 will then use the pointer to access the stored respectivepacket located in the packet buffer area 224 (block 358). The hostprocessor 220 will then process the accessed data packet (block 360).

However, if the host processor 220 determines that the DMA descriptor isclassified as a special DMA descriptor 236 (block 354), the hostprocessor 220 will proceed to read the connection state information ofthat TCP packet contained in the special DMA descriptor 236 (block 362).The host processor 220 will then process the accessed connection stateinformation (block 360) directly from the special DMA descriptor 236without having to expend computational resources to access the packetbuffer area 224 of the buffer memory 219 to retrieve this information.It should be noted that the above functions are generally described asbeing performed by the network traffic management device 110 may beperformed by the network interface controller 200, the host processor220 or a combination of the two components.

Having thus described the basic concepts, it will be rather apparent tothose skilled in the art that the foregoing detailed disclosure isintended to be presented by way of example only, and is not limiting.Various alterations, improvements, and modifications will occur and areintended to those skilled in the art, though not expressly statedherein.

Although the above description is directed to connection statusinformation in TCP packets, the system and method may be applied to anyother protocols which have data packets that contain information whichis to be immediately consumed in the network traffic management device.Such information includes, but is not limited to, event information,ICMP error messages, and the like. For example, different non-TCP basedprotocols that utilize DMA may use the described processes. Although,the examples above relate to networks, the processes may also be usedfor both network based and non-network based protocols such as storageprotocols. Any protocol requiring the DMA of state information withoutbulk data may use the direct DMA process. These alterations,improvements, and modifications are intended to be suggested hereby, andare within the spirit and scope of the examples. Additionally, therecited order of processing elements or sequences, or the use ofnumbers, letters, or other designations therefore, is not intended tolimit the claimed processes to any order except as may be specified inthe claims.

What is claimed is:
 1. A method for efficiently processing a receiveddata packet, the method comprising: determining, by a network trafficmanagement device, when a received data packet contains connection stateinformation; extracting, by the network traffic management device, theconnection state information from the data packet when the data packetis determined to contain the connection state information; storing, bythe network traffic management device, the data packet in anon-contiguous packet buffer area and the connection state informationextracted from the data packet as a special Direct Memory Access (DMA)descriptor in a contiguous ring buffer area configured to be capable ofbeing accessible by a host processor, the stored connection stateinformation comprising at least a state indicator; and notifying, by thenetwork traffic management device, the host processor that the specialDMA descriptor has been stored, wherein the stored connection stateinformation from the special DMA descriptor is configured to be capableof retrieval by the host processor.
 2. The method of claim 1, whereinthe data packet is a Transmission Control Protocol (TCP) data packet. 3.The method of claim 1, further comprising: discarding, by the networktraffic management device, the data packet after storing the connectionstate information.
 4. The method of claim 1, further comprising:writing, by the network traffic management device, the connection stateinformation as the special DMA descriptor prior to storing the specialDMA descriptor.
 5. The method of claim 1, further comprising: storing,by the network traffic management device, the data packet in a packetbuffer area when the data packet is determined not to contain connectionstate information.
 6. A non-transitory computer readable storage mediumhaving stored thereon instructions for efficiently processing a receiveddata packet comprising machine executable code which when executed by aprocessor, causes the processor to perform steps comprising: determiningwhen a received data packet contains connection state information;extracting the connection state information from the data packet whenthe data packet is determined to contain the connection stateinformation; storing the data packet in a non-contiguous packet bufferarea and the connection state information extracted from the data packetas a special Direct Memory Access (DMA) descriptor in a contiguous ringbuffer area configured to be capable of being accessible by a hostprocessor, the stored connection state information comprising at least astate indicator; and notifying the host processor that the special DMAdescriptor has been stored, wherein the stored connection stateinformation from the special DMA descriptor is configured to be capableof retrieval by the host processor.
 7. The medium of claim 6, whereinthe data packet is a Transmission Control Protocol (TCP) data packet. 8.The medium of claim 6, further having stored thereon instructions thatwhen executed by the processor cause the processor to performs stepsfurther comprising: discarding the data packet after storing theconnection state information.
 9. The medium of claim 6, further havingstored thereon instructions that when executed by the processor causethe processor to performs steps further comprising: writing theconnection state information as the special DMA descriptor prior tostoring the special DMA descriptor.
 10. The medium of claim 6, furtherhaving stored thereon instructions that when executed by the processorcause the processor to performs steps further comprising storing thedata packet in a packet buffer area when the data packet is determinednot to contain connection state information.
 11. A network trafficmanagement device comprising: a processor; a memory coupled to theprocessor and configured to be capable of executing programmedinstructions comprising and stored in the memory to: determine when areceived data packet contains connection state information; extract theconnection state information from the data packet when the data packetis determined to contain the connection state information; store thedata packet in a non-contiguous packet buffer area and the connectionstate information extracted from the data packet as a special DirectMemory Access (DMA) descriptor in a contiguous ring buffer areaconfigured to be capable of being accessible by a host processor, thestored connection state information comprising at least a stateindicator; and notify the host processor that the special DMA descriptorhas been stored, wherein the stored connection state information fromthe special DMA descriptor is configured to be capable of retrieval bythe host processor.
 12. The network traffic management device of claim11, wherein the data packet is a Transmission Control Protocol (TCP)data packet.
 13. The network traffic management device of claim 11,wherein the processor is further configured to be capable of executingprogrammed instructions comprising and stored in the memory to: discardthe data packet after storing the connection state information.
 14. Thenetwork traffic management device of claim 11, wherein the processor isfurther configured to be capable of executing programmed instructionscomprising and stored in the memory to: write the connection stateinformation as the special DMA descriptor prior to storing the specialDMA descriptor.
 15. The network traffic management device of claim 11,wherein the processor is further configured to be capable of executingprogrammed instructions comprising and stored in the memory to: storethe data packet in a packet buffer area when the data packet isdetermined not to contain connection state information.